Conventionally, it is known that an image picked up by an image input apparatus such as a camera is differently viewed depending on a visual environment at the time of observation, and there are cases where images are not reproduced with desired colors. This occurs when the color rendition under a light source at the time of image pick-up (hereinafter referred to as “the image pick-up light source”) and the color rendition under a light source at the time of observation (hereinafter referred to as “the observation light source”) greatly differ from each other, and so on. For example, when the image picked up under a D65 light source of a sunlight type has been observed under an F5 light source of a high-efficiency fluorescent lamp type, the reproduced colors greatly differ from each other.
Further, it is known that color reproduction can be excellently made between light sources of the same type by performing correction called “white balance” to reproduce a white color of the picked-up image as it is. Here, needless to say, it is of course necessary that the image pick-up light source be estimated with high accuracy. Conventionally, the white balance technique is adopted as the color reproduction correcting method.
On the other hand, a light source of a sunlight type is known for having a high level color-rendering property and a light source of a fluorescent lamp type is known for having a low level color-rendering property. However, there is also a demand for reproducing the image picked up under a light source of a fluorescent lamp type with a color rendering property under a light source of a sunlight type.
However, the white balance is a technique which performs correction to reproduce an achromatic color as it is. Therefore, in a case where the color rendition of the image pick-up light source and that of the observation light source greatly differ, there is a problem that the chromatic colors may not be excellently reproduced by the color reproduction correcting where only the white balance is used.
Also, in a case where a correction coefficient is prepared for every image pick-up light source and observation light source to perform color reproduction correction, there is a problem that the processing must be extremely complicated.
The present invention has been made in view of the above-described problems and an object of the invention is to provide a color reproduction correcting device and a color reproduction correcting method for an image input apparatus, in which colors are excellently reproduced without difficulties even when the image has been reproduced under an observation light source whose color rendering property is different from that of the image pick-up light source.